Over the last 1 1/2 to 2 yrs our elkhound (12yrs old) Theo has decided drinking from the toilet is better than drinking form his water dish.  Also drinking from the water dish out side is better than his inside dish.  I thought if I put his water dish up on a little platform that would help.  Nope he dragged the dish off spilling water over the floor.   Why do dogs like toilet water?  
The wife has a fit every time she sees Theo doing it.  We are going to try different water and food dishes just in case there is something wrong with his current ones.

It's colder.

My dogs do the same thing. My lady thinks its not big deal, until they come give here a big kiss after I just dominated the toilet. I remind her every time.

Close the lid!

This and +1 to keeping the toilet lid down...

Stop being lazy and close the lid.  And remove other water bowls outside.  If you only give the dog the option of drinking out of 1 bowl inside, he'll get thirsty enough and relent.

Really dogs don't care about the temp of the water for drinking....some dogs if over heated will stand in cold water as it cools them quick...their feet really shed the heat.

Back to the toilet, whatever you do don't put anything in the toilet as far as cleaners, dies, anything....and a dog that size is not likely to respect the lid being down...they can figure it out.

I am going to say one of two things.....he is getting up there in age and it just hurts to bend that far down, but you did say you tried to raise the level of his dish.

Or it is just that much bigger then his normal bowl and that is just easy for him

Or...the water is just fresher.....yea, that really comes into it....and think about it....dogs have about 1/3 the taste that humans do, so stuff that would really make us puke are nothing to a dog.

If you keep the bowl free of any cleaners there is no harm to the animal....the only way to really keep them out once they have discovered the source is to close the door.

It really isn't a temp thing, prob water is just fresher - or the bowl isn't as fresh and needs washed.

Mine will open the toilet seat if I leave it down, have also caught him turning on the water in the tub to get a drink more than once.

Life with a dog that is smarter than you isn't easy...

that's funny

Get a Great Dane, never an issue.  (being smarter than you)

I was in the family room today and heard the dog walk into the bathroom(tile floor).    The Wife walked in right behind him and started lecturing him about drinking from the toilet.  She told him to get out and never to drink from the toilet again.  She then made him sit by his water bowl until she got fresh water.   He must of just sat there because I heard the wife go UUUUGGG and stomp off.  After she left I heard the dog go back into the bathroom for a drink unfortunately for the dog the toilet seat was now down.